Plastic bucket and lid

ABSTRACT

A plastic bucket includes at least one undercut adjacent an upper end of the bucket defined by a bucket wall which extends upwardly and inwardly along a diagonal path. An annular, vertical section may be provided at the upper end of the diagonal path. Above the vertical section, the bucket wall extends radially outwardly to create an annular, horizontal flange. In addition, an uppermost annular rim may extend upwardly from the horizontal flange and be located approximately midway between inner and outer radii of the flange

BACKGROUND OF THE INVENTION

[0001] Many designs of plastic buckets and lids are well-known, see forexample the following patents of John W. Von Holdt: U.S. Pat. Nos.4,375,948; 4,574,974; 4,512,494; 4,512,493; 4,452,382; 4,380,305;4,308,970; and 4,210,258.

[0002] Many containers, such as cans for food, paint and other solventsand chemicals have also been made of plastic, as shown in theabove-cited patents. However, plastic buckets of course lack thestrength of metal buckets, so that in many cases special designs of theplastic buckets must be used to obtain, for example, a desired level ofhoop strength about the mouth of the plastic bucket. This hoop strengthis achievable in the prior art by reinforcement in some manner of themouth area of the plastic bucket, typically involving an annular portionthat projects radially inwardly, which reinforces the bucket.

[0003] However, buckets of this design typically require a collapsiblecore for their molding, which adds capital and operating expense to theoperation, and also tends to slow the operation down. Likewise,collapsible cores are subject to failure and other problems, whichfurther slows the efficiency of the operation.

[0004] In accordance with this invention, a plastic bucket is providedwhich does not require manufacture by the use of a collapsible core. Atthe same time, the bucket has a desired amount of hoop strength, even aplastic bucket which is of the shape of a conventional metal paint can.

DESCRIPTION OF THE INVENTION

[0005] By this invention, a plastic bucket defines an annular lip and anattachable plastic lid. The lid defines a peripheral, outer annular wallwhich defines an outer wall of an annular recess of the lid. The bucketlip occupies the recess in locked, sealed relation with the lid.

[0006] A principal object of the present invention is to provide aunique design for the upper end of a plastic container comprising anannular undercut section, an annular vertical wall portion above theundercut section, an annular horizontal ledge above the annular verticalwall, and an upright annular rim at the uppermost end of the bucketwhich rim is positioned approximately centrally with respect to theannular horizontal ledge.

[0007] In a preferred embodiment, the foregoing bucket is provided withonly a single undercut section which facilitates its molding and permitsit to be molded without use of a collapsible mold core, preferably byusing a mold of the type described in my U.S. Pat. No. 4,375,948.

[0008] The foregoing novel bucket design has been proven by extensivetesting to afford surprisingly improved hoop strength and stackingstrength. Such improved strength characteristics are so significant thatit is possible with such a bucket design to eliminate all external ribsor rings which are commonly used to provide hoop strength such as shownin Holt U.S. Pat. No. 3,977,563 and Letica U.S. Pat. No. 4,349.119. Theeliminating of all such external ribs and or rings, as well as theelimination of any internal ribs, provides an exceptionally clean andsimple design which is easy to mold and offers numerous advantages tothe users of such plastic buckets.

[0009] The present invention is not limited to the use of a singleundercut, but for most applications that is the preferred embodiment. Itis definitely preferred to mold the foregoing bucket without use of acollapsible mold core, and my preferred mold is of the type shown in myU.S. Pat. No. 4,375,948, but other molds may possibly be used in certainapplications.

[0010] The invention is also not limited to a design which has noexternal or internal ribs, but my preferred embodiment has no externalribs and preferably has no internal ribs because my unique bucket designprovides the desired hoop strength and stacking strength without theneed for the increased strength which such ribs commonly provide.Nevertheless, certain alternative embodiments which employ external orinternal ribs will be described herein.

DESCRIPTION OF THE DRAWINGS

[0011] Referring to the drawings, FIG. 1 is a perspective view of amolded bucket and attached lid in accordance with this invention;

[0012]FIG. 2 is an enlarged, fragmentary, transverse sectional viewthrough the bucket lip and the periphery of the lid of the bucket, takenalong line 2-2 of FIG. 1;

[0013]FIG. 3 is an enlarged, fragmentary, elevational view of the lidand upper portion of the bucket of FIG. 1, showing a portion of a tearstrip;

[0014]FIG. 4 is a fragmentary, enlarged, longitudinal sectional view ofanother embodiment of a bucket and lid;

[0015]FIG. 5 is a fragmentary, enlarged, elevational view of a portionof the bucket of FIG. 4;

[0016]FIG. 6 is a vertical sectional view taken along the line 6-6 ofFIG. 8 showing an alternative embodiment of the invention where a singleundercut is provided at the upper end of the container and a pluralityof internal reinforcing ribs are formed in the area of the undercut butno external ribs are provided as in the earlier embodiments;

[0017]FIG. 7 is an enlarged fragmentary view showing the upper end ofthe container of FIG. 6;

[0018]FIG. 8 is a view looking upwardly along the line 8-8 of FIG. 7showing a plurality of internal ribs spaced around the interior wall ofthe container near the upper end thereof;

[0019]FIG. 9 is a fragmentary vertical section showing anotheralternative embodiment of the invention having a single undercut at theupper end and having an offset at the upper end of the undercut as shownin the embodiment of FIG. 4, there being provided internal ribs in thearea of the undercut as in the embodiment of FIGS. 6-8 without the useof any external ribs in the undercut area, and there being shown one oftwo bale ears for holding a molded handle;

[0020]FIGS. 10 and 11 are top and side elevational views of a bucket ofthe type generally described herein but showing the addition of aplastic handle which is molded during the molding operation to mold thebucket;

[0021]FIG. 12 is a fragmentary vertical section showing a preferredembodiment of the present invention which is similar to the embodimentof FIG. 4 and also to the embodiment of FIG. 9 but it has no external orinternal ribs because the bucket design affords the necessary strengthwithout such ribs;

[0022]FIG. 13 is a fragmentary perspective view showing an interruptionor slot formed in the radially outer portion of the horizontal flangeformed beneath the uppermost rim of the bucket; and

[0023]FIG. 14 is a fragmentary vertical section taken along the line A-Aof FIG. 13.

[0024] Now, in order to acquaint those skilled in the art with themanner of making and using my invention, I shall describe, inconjunction with the accompanying drawings, certain preferredembodiments of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0025] Referring to FIGS. 1-3, a plastic bucket 10 having an attachedlid 12 is shown, each of the lid and bucket being manufactured byinjection molding from known plastic compositions.

[0026] Bucket 10 is shown to comprise an annular lip 14 which definesthe bucket mouth across which lid 12 extends. Lid 12, in turn, defines aperipheral, outer annular wall 16 which, with annular, inner lid wall 18and annular bridging wall 20, defines an annular recess which isoccupied by bucket lip 14 in locked, sealed relation with lid 12.

[0027] Outer, annular lid wall 16 also defines a circumferential tearstrip 22, which extends almost completely about the circumference of lidwall 16 or being continuous about that wall, terminating at one end witha free handle 24 which is partly surrounded by a space 26, so thathandle 24 may be grasped and pulled to cause circumferential tearing ofthe circumferential tear line 28. Upon removal of tear strip 22, theremainder of outer wall 16 may be pried outwardly with relative ease foropening of the lid.

[0028] Inwardly extending projections 30 are provided in known manner,being intermittently spaced about the periphery of lid wall 16 or beingcontinuous about that wall to engage the undersurface of bucket lip 14,as shown in FIG. 2.

[0029] Thus, after removal of tear strip 22, the bucket lid is readilyopened and reclosed as desired.

[0030] Additionally, bucket 10 defines a plurality of outwardly anddiagonally extending ribs 32, which are an integrally molded part of thebucket 10 and which intersect each other in criss-cross relation. Theseribs are positioned entirely around the periphery of bucket 10, andserve to increase the hoop strength of the bucket.

[0031] Also, bucket 10 is shown to define three outwardly extending,integral rings 34 which intersect the diagonal ribs 32, and thus alsocontribute to improving the bucket's hoop strength in the vicinity ofthe bucket lip.

[0032] Thus, buckets 10 can be molded which, although made of plastic,can have hoop strength that is comparable with metal buckets, yet whichare better than metal buckets in their resistance to pop off of the lid,when the bucket is dropped and the like. Appropriate fins or vanes 36may be provided to strengthen lid 12 as may be desired. Also, internalfins or vanes 38 may be provided to bucket 10 for a similarstrengthening purpose.

[0033] Also, it can be seen that bucket 10 defines only one annular,diagonal undercut 39, so that rings 34 may be provided without exceedingthe main diameter of the bucket. This permits the use of such a bucketin conventional filling machinery and the like. Also, such a bucket, inwhich the inward extent of the undercut 39 is no more than aboutone-quarter inch, or not over 6% of the bucket diameter can bemanufactured with a mold core which is not collapsible, such as the moldshown in U.S. Pat. No. 4,375,948. The bucket of preferred designs asshown can be popped off of the mold core.

[0034] Referring to FIGS. 4 and 5, a molded bucket 10 a carries a lid 12a which is of generally similar design to the previous embodiment exceptas otherwise shown herein.

[0035] As before, lid 12 a defines an outer annular wall 16 a which, inconjunction with inner annular wall 18 a and annular bridging wall 20 a,defines an annular recess for the securance of bucket lip 14 a.

[0036] In this particular embodiment, bucket lip 14 a is carried upon aflange 40 which extends outwardly and is carried by the bucket. Flange40 defines an annular recess 42 in which the lower edge 44 of outer,annular lid wall 16 a is “buried”, to prevent one who desires to openthe container from prying the lid 12 a off of the bucket with a screwdriver or the like. Thus, lid 12 a is permanently attached to bucket 10a until the removal of tear strip 22 a is accomplished.

[0037] Tear strip 22 a may be of similar design to tear strip 22 of theprevious embodiment When it has been circumferentially removed bytearing along tear line 28 a in similar manner, the remaining portion ofouter, annular wall 16 a is easily removed either with the fingers or ascrew driver. Inwardly extending projection 30 a may be continuous andannular, or it may be intermittent along the circumference for easieropening of lid 12 a.

[0038] A single undercut 39 a is provided in bucket 12 a also, similarto the previous embodiment. This provides a recess in which diagonalvanes or ribs 46 may be provided, extending in a diagonal, crisscrossmanner as illustrated by FIG. 5. This provides significantly increasedhoop strength to bucket 12 a. Also, a label 48 may be placed over thecrisscross ribs 46 if desired by automatic label applying machinery.

[0039] The resulting container is tamper proof because of the requireduse of tear strip 22 a to open it, and exhibits a high hoop strength foravoiding inadvertent lid pop off when the container is dropped or thelike.

[0040] Reference is now made to the embodiment of FIGS. 6-8 where abucket or container 100 has a container wall 102 which slopes inwardlyat its upper end as best shown at 103 in FIG. 7 to provide a singleundercut area shown at 104. In this embodiment, no external ribs areformed in the undercut area 104, but internal ribs are provided as shownat 106. FIG. 8 shows the internal ribs 106 as being generally radial andspaced around the entire inside circumference of the upper end of thebucket or container.

[0041] The upper end of the container 100 differs from the containershown in FIG. 2 because it has an offset in the container wall above thesingle undercut, generally as shown in FIG. 4. Thus, referring to FIG.7, the container wall 102 slopes inwardly at 103 to form the offset 104and then extends upwardly again at 108 and then outwardly to form anoffset 110. Finally, the container wall extends upwardly again at 112 todefine the open mouth of the container. The offset 110 provides anadvantage in that it affords increased hoop strength for the upper endof the container.

[0042] In order to facilitate the molding of a plastic bucket inaccordance with the present invention, and avoid the need for acollapsible mold core, it is necessary to limit the magnitude of theundercut such as shown, for example, at 104 in FIG. 7 or at 104′ in FIG.9, i.e., the amount that the wall shown at 108 in FIG. 7 is radiallyoffset from the wall shown at 102. The deeper the offset, the moredifficult it is to mold a bucket without use of a collapsible mold core.

[0043] Generally speaking, the magnitude of the undercut should notexceed approximately 5% or 6% of the diameter of the container. Forexample, with a larger container having a diameter of 12 inches, it ispreferable that the undercut not extend inwardly more than about ¾ inch.However, for a smaller container, the undercut may comprise a largerpercentage of the diameter. For example, with a container having a 2inch diameter, it is preferable that the undercut not extend inwardlymore than ⅜ inch.

[0044] For most containers, it is preferred that the undercut not exceed⅜ of an inch, but for containers of larger size, such as 12 inchdiameter, the undercut may extend inwardly as much as ¾ inch. Thecritically important advantage of the use of an undercut in the presentinvention is that by using only a single undercut, and controlling themagnitude of the undercut, it is possible to mold the container withoutuse of a collapsible mold core.

[0045] Reference is now made to FIG. 9 which shows an embodiment similarto the embodiment of FIGS. 6-8 with corresponding components identifiedwith corresponding primed numerals. In FIG. 9, the container wall 102′slopes inwardly at 103′ and then upwardly at 108′, and it then extendsoutwardly again at 110′ to form an offset for added hoop strength as inthe prior embodiment. The single undercut 104′ has no external ribs, butinternal ribs are provided at 106′ as in the embodiment of FIGS. 6-8.The vertical wall portion 108′ is somewhat longer than in the embodimentof FIGS. 6-8. In addition, FIG. 9 shows one of two opposed bale ears 122which serve for mounting a handle as will be described below. A similarbale ear is shown at 124 in FIG. 6, the opposite one not being shown inFIG. 6 due to the section line 6-6 in FIG. 8.

[0046]FIGS. 10 and 11 show a further embodiment of a container includinga handle 130 which is pivotally connected to opposite sides of thebucket as shown at 132. The bucket shown at 134 is similar to theexternal rib embodiments described earlier herein, the principaldifference being the addition of the handle 130 which can be moldedduring the molding of the bucket.

[0047] Reference is again made to the embodiment of FIGS. 1-3, and theembodiment of FIGS. 4-5. It should be understood that while the radiallyinwardly projecting ribs 38 are shown only in FIG. 2 which is part ofthe embodiment of FIGS. 1-3, the description of the embodiment of FIGS.4-5 indicates that the same features of the embodiment of FIGS. 1-3 areincluded except as otherwise described, so the intent is that theembodiment of FIGS. 4-5 may include the internal radially inwardlyprojecting ribs shown at 38 in FIG. 2.

[0048] Reference is now made to FIG. 12, which shows a preferredembodiment of the present invention. In FIG. 12, the upright containerwall 200 slopes inwardly at 202 and then upwardly at 204, and it thenextends outwardly again at 206 to form a horizontal, annular flangewhich together with vertical section 204 affords very substantial hoopstrength and stacking strength. An uppermost annular, vertical rim 208,designed to cooperate with a lid (not shown) as generally shown in FIG.2, extends up from horizontal, annular ledge 206 from a radius which isapproximately midway between the inner and outer radii of the horizontalledge 206.

[0049]FIG. 12 shows the uppermost, annular rim 208 being positionedapproximately midway between the inner and outer radii of thehorizontal, annular flange 206. The foregoing approximate location ofrim 208 relative to horizontal flange 206 is desirable in manyapplications. However, there is a further consideration which is thatfor optimum strength characteristics it has been found desirable tolocate the uppermost rim 208 so that the radially inner wall of rim 208is not radially inwardly of the radially outer wall of vertical section204. As shown in FIG. 12, the radially inner wall of uppermost rim 208is slightly radially outwardly of the radially outer wall of verticalsection 204, which has proved to be a desirable relative position foruppermost rim 208. Thus, while the rim 208 may be located radiallyinwardly from the position shown in FIG. 12, it preferably should not belocated so its radially inside wall is radially inwardly of the outsideof upright wall 204.

[0050] There are no outer ribs located in the section defined by theundercut 202, as for example, in the embodiment of FIG. 2. Also, thereare no internal ribs radially inwardly of the undercut wall 202 as inthe embodiment of FIG. 2 or the embodiment of FIG. 9. The preferreddesign shown in FIG. 12 is free of external and internal ribs. Asexplained previously, the design of the bucket comprising undercut 202,vertical section 204, horizontal flange 206 and upper, vertical rim 208provides unexpected strength sufficient so that additional strengthwhich the ribs afford is not needed.

[0051] While the present invention is not limited to a bucket having noexternal or internal ribs, the design shown in FIG. 12 which has no ribsis the preferred embodiment because it affords a clean and simple designwhich is easy to mold and which is extremely advantageous for certainapplications such as for a one-gallon plastic paint can. The preferredembodiment shown in FIG. 12 has only a single undercut, which makes thebucket easier to mold without using a collapsible mold core, but thepresent invention may also be used with a bucket which has more than oneundercut.

[0052] It is highly desirable that the angle of the undercut wall 202,i.e., the angle the wall defines with the vertical, be controlled so asnot to exceed 45 degrees. If the foregoing angle exceeds approximately45 degrees, it may not be possible to mold the bucket without using acollapsible mold core, especially if more than one undercut is used asin Letica U.S. Pat. No. 4,349,119. The angle for the wall 202 isapproximately 30 degrees, as shown in FIG. 12, and a preferred range forsuch angle is between approximately 30 degrees and 45 degrees. However,satisfactory results may be obtained using an angle in the range of 20degrees to 50 degrees.

[0053] I prefer a range of 30 degrees to 45 degrees for the angle whichdiagonal wall 202 defines with a vertical. A smaller angle can havedisadvantages because if you wish to maintain the depth of the undercut,a smaller angle means that the vertical height component of the diagonalwall 202 will be greater, and in that case the upright bucket wall 200will have less height. Since the upright wall 200 is often used forcarrying a label, it may be a disadvantage in some applications toreduce its height significantly from what is shown in FIG. 12.

[0054] The general purpose of the undercut is to produce hoop strength,and the vertical section 204 combined with the horizontal flange 206affords exceptional hoop strength to a degree which permits eliminationof external and internal ribs. As a result, if one were to reduce theangle which diagonal wall 202 makes with a vertical, one would in mostcases not want to significantly reduce the depth of the undercut shownin FIG. 12, and because in many applications it is not desirable tosubstantially increase the vertical height component of the diagonalwall 202, it is preferred in such applications to avoid reducing theangle between diagonal wall 202 and a vertical to much less than 30degrees.

[0055] The combination of the undercut 202, upright or vertical, annularsection 204, horizontal, annular ledge 206, and uppermost, annular rim208 located approximately midway between the inner and outer radii ofledge 206, affords surprisingly increased hoop strength and stackingstrength. FIG. 12 has the actual dimensions of the bucket wall shown ininches. The dimensions shown are for a one-gallon plastic bucket andwill change for larger and smaller buckets. While the invention isclearly not limited to particular dimensions, the relative positioningand relative dimensions of the structural components 202, 204, 206 and208 are important, and the particular design shown in FIG. 12 isconsidered a particularly advantageous arrangement.

[0056] While no lid is shown in conjunction with the preferredembodiment of FIG. 12, a lid of the general type including a tear stripas shown in FIG. 4 may be used, although it is not necessary that thelower edge of the lid wall be buried in the manner shown in FIG. 4.

[0057]FIGS. 13 and 14 show an interruption or slot formed at 220 in theradially outer portion of annular, horizontal flange 206 While such slot220 will create a small amount of weakness, it serves the purpose ofproviding room for someone to insert their fingers beneath the outerwall of a lid for the purpose of removing the lid. Accordingly, for manyapplications the minor reduction in strength caused by the slot at 220in the horizontal flange 206 is acceptable in order to facilitate manualremoval of a lid.

[0058] Another feature shown in FIG. 12 concerns the thickness of thediagonal wall 202 and the vertical wall 204 compared to the outermostbucket wall 200. As shown in FIG. 12, both the diagonal wall 202 and theupright wall 204 are somewhat thicker than the main bucket wall 200. Thereason for increasing the wall thickness of walls 202 and 204 is becausethe offset created by diagonal wall 202, while designed to increase hoopstrength, will reduce stacking strength. As a result, when such anoffset is used to create a substantial undercut, it is preferable thatthe wall 202, and in some cases also the wall 204, be made of increasedthickness compared to main bucket wall 200 for the purpose ofmaintaining stacking strength. In the foregoing manner, excellent hoopstrength and stacking strength may be obtained.

[0059] There are prior art patents which teach designs for plasticbuckets and which provide various structure for the purpose of affordinghoop strength and stacking strength. However, such prior art patents donot teach the present invention and fall far short of providing theadvantages of the present invention, especially with respect to thepreferred embodiment shown in FIG. 12.

[0060] Letica U.S. Pat. No. 4,349,119 in FIG. 5 shows a bucket designhaving a double undercut, one undercut being shown at 75 and a secondundercut being shown at 106. The second undercut shown at 106 makesmolding more difficult, especially since the angle from the verticalappears to exceed 45 degrees, and the Letica structure is madecommercially from a collapsible mold core.

[0061] In addition, Letica shows a plurality of external rings or ribs68, and generally the upper end of the Letica bucket differs markedlyfrom the present invention, as can readily be seen by comparing FIG. 5of Letica with FIG. 12 of the present invention.

[0062] Buc U.S. Pat. No. 4,524,882 shows a bucket design in FIG. 4having a single undercut at 15 and a so-called bridge member 18 whichpresumably provides hoop strength. However, the Buc design fails toinclude any structure resembling the upright or vertical, annularsection shown at 204 in FIG. 12 of the present invention which islocated intermediate the undercut wall 202 and the horizontal, annularledge 206, and which contributes in a major way to the hoop strength andstacking strength of the design shown in FIG. 12. In FIG. 12, thecombination of sections 204 and 206 provides an annular L-shapedstructure which offers unexpected advantages with respect to hoopstrength.

[0063] In addition, the extreme upper end of the Buc bucket is quitedifferent from the FIG. 12 design since it provides upright rim portionsat the radially inner and outer edges of member 18 as opposed to theFIG. 12 design where a single annular rim 208 is approximately midwaybetween the radially inner and outer portions of horizontal, annularledge 206. Also, the Buc patent is merely a paper patent, and the designshown therein has never been used commercially.

[0064] One further prior art patent is Holt U.S. Pat. No. 3,997,563.FIG. 1 of Holt appears to show an undercut, although that structure isnot shown in the other drawings. The upper end of the Holt bucket isentirety different from the design shown in FIG. 12 of the presentinvention and it comprises in essence an upright annular wall 10 withtwo annular rigs or ribs 18 on the outside, and an uppermost rim whichextends up from the radially inner edge of the ring 18. There is littleif any similarity between the Holt design and the FIG. 12 design of thepresent invention.

What is claimed is:
 1. A plastic bucket comprising, in combination: anupright, annular bucket wall terminating in an annular lip to form anopen bucket mouth, said annular lip comprising a single annular wallportion extending upwardly from said bucket wall radially inwardly alonga diagonal path to an upper end, said annular lip further extending fromsaid upper end in an upright vertical direction generally parallel tothe bucket wall to form a first vertical wall section having a radiusover the range of the thickness thereof less than the radius of saidbucket wall over the range of the thickness thereof, said annular lipalso consisting comprising a vertical rim generally parallel to saidfirst vertical wall section and having an inside and an outside, theinside having radius less than the radius of said annular bucket walland greater than the radius of said vertical wall section; and a single,generally horizontal connection ledge extending from the first verticalwall section between and connecting the first vertical wall section andthe vertical rim.
 2. A plastic bucket as defined in claim 1 where noexternal ribs or rings are formed on said annular lip in the area ofsaid undercut.
 3. A plastic bucket as defined in claim 1 where nointernal ribs are formed on said annular lip in the area of saidundercut.
 4. A plastic bucket as defined in claim 1 where the anglebetween said diagonal path and the vertical direction does not exceedapproximately 45 degrees.
 5. A plastic bucket as defined in claim 1where no external or internal ribs or rings are formed on said annularlip in the area of said undercut.
 6. A plastic bucket as defined inclaim 1 where said first vertical wall section has a height which isless than the width of said horizontal connection ledge and is less thanthe length of said diagonal path.
 7. A plastic bucket as defined inclaim 1 where said horizontal connection ledge has a width which exceedsone-half of the distance between the bucket wall and the horizontalconnection ledge.
 8. A plastic bucket as defined in claim 1 where themagnitude of radially inward extent of said annular wall portion iscontrolled to permit said bucket to be molded without the use of acollapsible mold core.
 9. The combination of claim 1 wherein saidhorizontal wall projects radially beyond said vertical rim.